Question

Which of the following is a reducing sugar?

• A. Galactose
• B. Gluconic acid
• C. $\beta$ -methyl galactoside
• D. Sucrose

Answer 1

The correct option is A Galactose

A reducing sugar is any sugar that is capable of acting as a reducing agent because it has a free aldehyde group or a free ketone group. All monosaccharides are reducing sugars, along with some disaccharides, oligosaccharides, and polysaccharides.
In the give options, only Galactose which is a monosaccharide sugar has a free aldehyde group.
Gluconic acid is an organic acid, $\beta$ -methyl galactoside is a glycoside containing methyl galactose and Sucrose is a disaccharide composed of glucose and fructose. All of these organic compounds lack a free aldehyde group or a free ketone group that can act on a reducing agent.